That synthetic, and even many natural, organic polymers require stabilization against light, particularly ultraviolet light, and heat induced discoloration and deterioration of physical properties is well known. Organic polymers subjected to outdoor exposure often discolor and show a loss of physical properties as a result of the exposure to a combination of degradation inducing factors (e.g. ultraviolet light, heat, water and oxygen). Outdoor use of organic polymers not only subjects the polymers to the ultraviolet light of the sun but also the heat of the sun. This outdoor exposure to the ultraviolet light and heat of the sun takes place in the presence of oxygen in the air. Thus, there can exist various combinations of factors working to degrade the organic polymer. On the other hand there exists other uses of organic polymers which result in their exosure to heat and oxygen in the absence of ultraviolet light, or ultraviolet light and oxygen in the absence of heat or even heat in the absence of oxygen. Thus, many organic polymers require protection against deterioration induced by a variety of environmental conditions. Factors such as heat and oxygen are not only present during the commercial use of organic polymers but are also present during the processing of the polymer into finished articles of commerce. Stabilization of organic polymers against discoloration and loss of physical properties during processing into finished products is also required.
In view of the numerous applications and large scale use of organic polymers, it is very important to stabilize such organic polymers against the deteriorating effects of environmental factors during processing and use. To protect many organic polymers against undesirable changes in physical properties and discoloration during processing and use, various stabilizers and stabilizer combinations have been added to the organic polymers. Included among such stabilizers are, for example, the well known metal salts, organometallic compounds, phenols, hindered phenols, substituted and unsubstituted benzophenones, salicylates, mercaptans, expoxides and benzothiazoles. More recently hindered amine stabilizers having tetraalkyl substituted piperidino groups have been proposed as stabilizers.
U.S. Pat. No. 4,279,804 to Cantotore et al., discloses the use of hindered amines as stabilizers against light, heat and oxidation for synthetic polymers. The Cantatore et al. hindered amines are compounds according to the formula: ##STR1## wherein:
R.sub.1 represents, inter alia, hydrogen or various hydrocarbon radicals;
R.sub.2, R.sub.3, R.sub.6 and R.sub.7 represent C.sub.1 -C.sub.6 alkyl;
R.sub.4 and R.sub.5 are hydrogen or C.sub.1 -C.sub.6 alkyl;
R.sub.8, R.sub.9, R.sub.10, R.sub.11, R.sub.12 and R.sub.13 are hydrogen or C.sub.1 -C.sub.6 alkyl;
n is 0 or 1; and
A represents, inter alia, &gt;CH--R.sub.18 where R.sub.18 is hydrogen, C.sub.1 -C.sub.20 alkyl, C.sub.5 -C.sub.12 cycloalkyl, phenyl, hydroxyphenyl, hydroxyphenyl substituted by 1 to 3 C.sub.1 -C.sub.4 alkyls, benzyl, or benzyl substituted by 1 to 3 C.sub.1 -C.sub.4 alkyls.
Although a large number of stabilizer compounds and stabilizer combinations, including the hindered amine type stabilizers have been proposed and some of them used, there continues the search for better stabilizers to overcome the deficiencies of known stabilizers. Among these deficiencies there are, for example, included low stabilizing efficiency, high cost, stabilizer instability, initial coloration of the polymer, volatility and odor. More effective, stable, easy-to-use and lower-cost stabilizers are always sought.
It is, therefore, an object of this invention to provide novel compounds having two bis(2,2,6,6-tetramethyl-4-piperidyl)-substituted heterocyclic rings. Another object of this invention is to provide, as highly effective stabilizer for organic polymer, compounds having two bis(2,2,6,6-tetramethyl-4-piperidyl)-substituted heterocyclic rings. A further object of this invention is to provide highly stable organic polymer compositions comprising an organic polymer and a compound having two bis(2,2,6,6-tetramethyl-4-piperidyl)-substituted heterocyclic rings. It is a still further object of this invention to provide a method of stabilizing organic polymers comprising the step of adding to an organic polymer, normally susceptible to deterioration, a stabilizingly effective amount of a compound having two bis(2,2,6,6-tetramethyl-4-piperidyl)-substituted heterocyclic rings.